setup_real_mode() copies the page-aligned size of the embedded real-mode
blob into low memory. However, real_mode_blob ends immediately before
real_mode_relocs, so the copy includes relocation data and potentially
other .init.data contents when the size of realmode.bin is not
page-aligned.

Pad real_mode_blob to a page boundary so the copy contains only the
real-mode binary and its padding.

Fixes: 084ee1c641a0 ("x86, realmode: Relocator for realmode code")
Signed-off-by: Thorsten Blum <blum@kernel.org>
---
 arch/x86/realmode/rmpiggy.S | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/realmode/rmpiggy.S b/arch/x86/realmode/rmpiggy.S
index c8fef76743f6..ce5350241238 100644
--- a/arch/x86/realmode/rmpiggy.S
+++ b/arch/x86/realmode/rmpiggy.S
@@ -12,6 +12,7 @@
 
 SYM_DATA_START(real_mode_blob)
 	.incbin	"arch/x86/realmode/rm/realmode.bin"
+	.balign PAGE_SIZE
 SYM_DATA_END_LABEL(real_mode_blob, SYM_L_GLOBAL, real_mode_blob_end)
 
 SYM_DATA_START(real_mode_relocs)

On September 17, 2026 4:49:27 AM PDT, Thorsten Blum <blum@kernel.org> wrote:
>setup_real_mode() copies the page-aligned size of the embedded real-mode
>blob into low memory. However, real_mode_blob ends immediately before
>real_mode_relocs, so the copy includes relocation data and potentially
>other .init.data contents when the size of realmode.bin is not
>page-aligned.
>
>Pad real_mode_blob to a page boundary so the copy contains only the
>real-mode binary and its padding.
>
>Fixes: 084ee1c641a0 ("x86, realmode: Relocator for realmode code")
>Signed-off-by: Thorsten Blum <blum@kernel.org>
>---
> arch/x86/realmode/rmpiggy.S | 1 +
> 1 file changed, 1 insertion(+)
>
>diff --git a/arch/x86/realmode/rmpiggy.S b/arch/x86/realmode/rmpiggy.S
>index c8fef76743f6..ce5350241238 100644
>--- a/arch/x86/realmode/rmpiggy.S
>+++ b/arch/x86/realmode/rmpiggy.S
>@@ -12,6 +12,7 @@
> 
> SYM_DATA_START(real_mode_blob)
> 	.incbin	"arch/x86/realmode/rm/realmode.bin"
>+	.balign PAGE_SIZE
> SYM_DATA_END_LABEL(real_mode_blob, SYM_L_GLOBAL, real_mode_blob_end)
> 
> SYM_DATA_START(real_mode_relocs)

Acked-by: H. Peter Anvin <hpa@zytor.com>